A power converter that performs the conversion of electrical power is one type of electrical equipment. For example, the power converter is used in a photovoltaic power generation system, etc. In the photovoltaic power generation system, the power converter converts direct current power input from a solar cell panel into alternating current power and outputs the alternating current power to an electric power system. Such a power converter is called, for example, a power conditioner.
In the power converter, the heat generation of the devices in the interior in the power conversion is suppressed by cooling the devices by using a fan, etc. Therefore, for a power converter mounted outdoors, the dust, salt, corrosive gas, etc., included inside the external air enters the power converter when is the converter exposed to the air; and the durability of the power converter undesirably decreases.
Therefore, the power converter is contained inside a sealed housing; and the temperature inside the housing is controlled using an air conditioner. Thereby, the exposure of the power converter to the external air can be suppressed; and the decrease of the durability of the power converter can be suppressed. Also, in the case where the temperature control is performed using the air conditioner, it is unnecessary to uselessly enlarge the housing; and the increase of the mounting surface area of the power converter also can be suppressed.
However, in the housing in which the temperature control is performed using the air conditioner, it is necessary to stop the operation of the air conditioner to protect the outdoor unit when the external air temperature becomes a prescribed value or less. Because the temperature of the devices undesirably increases in the case where the operation of the air conditioner is stopped, the operation of the power converter also must be stopped.
Therefore, in an environment where the external air temperature is low such as in a cold district, etc., the power converter cannot be operated. For example, in a photovoltaic power generation system, a state undesirably occurs in which the power converter cannot be operated because the external air temperature is low even though sufficient electrical power is being supplied from the solar cell panel. For example, the power generation efficiency undesirably decreases.
Accordingly, in the electrical equipment housing that contains the power converter, it is desirable for the power converter to be operable even in an environment having a low external air temperature while suppressing the decrease of the durability of the power converter.